Improved polyvinyl chloride propellant compositions



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IMPROVED POLYVENYL CHLRDE PROPELLANT This invention relates generally to Vexplosive compositions and specically -to propellants -useful in rocketry.

Explosives of the perchlorate-polyvinyl chloride type have for some time been known to be useful as propellants in rocketry. Heretofore this type of explosive has usually included a stabilizer such as barium and cadmium soaps of saturated fatty acids and a plasticizer such as di-octyl sebacate. This composition has the disadvantageous characteristic that its burning rate changes radically as the temperature and pressure change. Its burning rate changes at the rate of about 0.15 to 0.25% per degree Fahrenheit, between the temperatures -20 and +180 F. depending upon the pressure. Such variation in burning rate has heretofore disqualified this type of explosive lfor many applications in rocketry and elsewhere.

It is an object of the present invention to produce an ammonium perchlorate-polyvinyl chloride type of explosive composition having a desirable `stability of burning rate over a wide temperature and pressure range.

It `is a further object ofthe present invention 4to prepare an explosive composition that, when expended, has no objectionable residue remaining.

The present invention is predicated upon the discovery that the use of di-normal octa-decyl adipate in propellant compositions of polyvinyl chloride resin/perchlorate oxidizer type, markedly stabilizes the burning rate throughout a Wide range of temperatures and pressures. The dinormal octa-decyl adipatc may be and preferably is substituted in whole o-r in part for the plastlcizer heretofore used in such compositions.

Those skilled in the art of rocket propulsion will be enabled to further appreciate the present invention from the following disclosure considered in conjunction with the'graphical representations, indicated as follows:

FIGURE l is a Iseries of graphs showing the burning rate in relation to the combustion pressure for some of the compositions contemplated by the invention;

FIGURE 2 is a series of graphs plotting the burning rate versus pressure at various temperatures between -20 F. and 200 F. for one of the compositions contemplated by the invention;

FIGURE 3 is a graphical representation of the burning rate versus temperature at various combustion pressures between 750 p.s.i. and 2000 p.s.i. -for one of the compositions contemplated within the invention; and

FIGURE 4 is a graphical representation of -chamber pressure versus time in the combustion chamber (in milliseconds) between temperatures of F. and 200 F.

In accordance with the preferred embodiments of the invention, the composition consists of polyvinyl chloride resins, ammonium perchlorate, di-normal octa-decyl adipate with or without a chemical stabilizing agent and other additives. The proportions of the components are not critical so long as the ratio of polywnyl chloride to di-normal octa-decyl adipate be within the range of between about 3 to 2 and about 2 to 3 by weight, with such variations in these proportions as are normally to be expected in the course of work on such compositions -b-y persons skilled in the art. Furthermore, 5 to 10% of either plasticizer or resin may be replaced by various epoxies or other materials without sacrificing the burning 3,084,083 Patented Apr. 2, 1963 "ice rate stability. Moreover, addition of lsmall .amounts of carbon will raise the burning rate of the composition.

The compositions of the present invention have an average burning rate increase which varies less than 0.07% per degree Fahrenheit between the 'temperatures of -60 and +200 F., which is minute when compared to 0.15 to 0.25% per -degree for the `di-ootyl -sebacate/polyvinyl chloride/perchlorate type systems.

Specifically, the compositions of the present invention may comprise (indicated as percent by weight) a polyvinyl chloride (5 to 20%), cli-normal octa-decyl adipate (5 to 20%), an oxidizer (50 to 85%), a chemical stabilizer (0 to 1%) and other ingredients (0 to 10%).

The polyvinyl resins used in the present invention are those well known in the ar-t for the purpose, such las Geon 121 (polyvinyl chloride p-lastisol resin) or Opalon 410 (plastisol polyvinyl chloride resin), and other polyvinyl chloride resins which yield similar properties.

The chemical stabilizer used in the present invention may also be one commonly used in the art such as Ferro .l12-1f2-A, which is a mixture of the barium and cadmium salt-s of ricinoleic acid (containing 5.5% barium and 5.5% Vcadmium and having `a typical specific gravity of 1.01), although other chemical stabilizers may be used or the chemical stabilizer may be left outof the composition without altering the ballistic properties significantly.

Ammonium perchlorate is used as the oxidizing agent,

vbut other similar oxidizing agents may be substituted therefor. The particle size of the oxidizing agent, ie., ammonium perchlorate, does have some influence on burning rate, but the particle size has no inuence on the `temperature lsensitivity or temperature coefficient which is theslope of the burning .rate curve. However, in the .preferred embodiment, the ammonium perchlorate is finely ground.

The other materials added to the composition Vmay be any such material normally added toexplosive compositions, including, among others, carbon.

The following examples arer set .forth to exemplify the present invention, however, the scope of the invention is not to be limited thereto:

l Example l A composition comprising (indicated as percent by weight):

Percent Ammonium perchlorate 80.00 Polyvinyl chloride resin 9.75 Di-normal octa-decyl adipate p 9.75 yFerro l2l2-A 0.50

750 p.s.i. Tp=0.052%/ F. 1000 p.s.i Tp=0.056%/ F. 1500 p si Tp=0.069%/ F. 2000 p.s.i. TP=0.077%/ F.

From the graphin 'FIGURE 3, it is apparent that at a 'pressure of 2000 p.s.i., the composition has a burning rate,

at -60 F., of approximately 0.8 inch per second. At 200 F., the burning ratevis increased only about .15 inch per second, thereby indicating a burning rate increase of approximately 0.07% per degree Fahrenheit over a 260 degree temperature range. It can also be seen from FIGU-RE 3'that the rate at which the burning rate increases is very nearly constant regardless of pressure.

Example II Polyvinyl chloride resin is suspended in di-normal octadecyl adipate and Ferro 1212A and the resulting liquid is added to `tinely ground ammonium perchlorate in a Sigma blade mixer in the 'following proportions (indicated as percent by weight): v

v Percent Polyvinyl chloride 12.25 Y Di-normal octa-decyl adipate 12.25 Ferro l2l2-A 0.5 Ammonium perchlorate 75.00

and mixed until the perchlorate is uniformly distributed throughout the composition.

Example III The composition of this example was prepared in the same manner as that `of Example II, but contains the This composition was also Iprepared in a manner similar to that employed in Example 1I (proportions also indicated as percent by weight), but in Vaddition to the components present in Examples II and I'II, there has been added a small amount otfcarbon:

Percent Piyvinyr chloride 13.45 Di-norm-al octa-decyl adipate 13.45 Ferro 1212-A .50 Ammonium perchlorate 72.50 VCarbon .l0

ExampleV V 13.25 parts by weight of polyviny-l chloride Vare added to 13.25 parts of di-normal octa-.decyl adipate and onehalf part of Ferro 12l2-A. This liquid was then mixed with 72.5 parts ammonium perchlorate and one-half part carbon Iin a Sigma blade mixer, similar to the preparations of Examples Il through IV. A

Example VI This composition was prepared in a manner similar to that described for Example II ibut contained the following proportions of the components (as percent by weight):

Percent' Polyvinyl chloride 9.75 Di-octyl phthalate' 9.75 Ammonium perchlorate 80.00 Ferro 12l2-A .50

VIn Examples II through V, Vit can be` seen that the oxidizer percentage is below 80%. With a low percentage of oxidizer there is a loss of energy and likewise a decrease in the specific impulse Iof the propellant.

This

loss of energy and specilc impulse causes a pressure plateau, which can be seen from the graphical representation indicated in FIGURE l. It can be seen that there is a pressure plateau existing for substantially all of the compositions of Examples lIII through V at a pressure of 1000 p.s.i. However, such a pressure plateau is very desirable in many applications. It can also be seen from this graph that the yformulation of Example II wherein there is 75% oxidizer (ammonium perchlorate) that the pressure plateau is at a substantially lower pressure than theplateaus forthe formulations of Examples III Ithrough V (namely, at 750 p.s.i.). Likewise, it can be seen from FIGURE 2, which is the burning rate versus combustion pressure `for the formulation of Example I, Ythat there are substantially no pressure plateaus when the oxidizer (ammonium perchlorate) represents approximately 80%. Thus, it is apparent that when the oxidizer percentage is above 75%, then there will be substantially no pressure plateausrabove a minimum pressure of about 750 p.s.i., but there will be a constant, 'but substantially stable, rate of increase in the burning rate as the pressure becomes higher.

The family of curves, represented in FIGURE 4, were derived from oscillograph measurements of combustion pressure versus time in the combustion ch-amber of the composition of Example I. The difference of approximately 200 p.s.i. between the plateau pressures at 15 F. and 200 F. dramatically demonstrate the usefulness of the present invention in propellent systems operating over a range of temperatures from 60 F. to +200 F. This graph is not contrary to the preceding statements concerning burning rate versus pressure for this composition, but rather -shows the similarity of pressure patterns in the combustion chamber for the wide variance of ternperat-ures.

From the foregoing disclosure, those skilled in the art should readily understand that the invention is not limited to the specific embodiments shown but is also inclusive of the variations as suggested in various parts ofthe preceding paragraphs.

Having thus described the invention, what is claimed and desired to be secured Yby Letters Patent is:

1. An explosive composition consisting essentially of polyvinyl chloride resin, ammonium perchlorate and a plasticizer, the improvement being in the use of from 5-20% by weight di-normal octa-decyl adipate as the plasticizer. Y

2. An explosive composition having a substantially stable burning rate over a Wide temperature range consisting essentially of polyvinyl chloride resin (5-20% by weight) ammonium perchlorate (S0-85% by Weight), and di-normal octa-decyl adipate (5-20% by weight).

3. An explosive composition having a substantial stability of burning rate over a temperature range of from about F. to +200 F. consisting essentially of polyvinyl chloride resin (5-20% by weight), ammonium perchlorate (S0-85% by Weight), Ferro l2l2A (0-l% by weight) and di-normal octa-decyl'adipate (5-20% by Weight).

4. An explosive composition having an average burning rate increase of less than 0.07% per degree Fahrenheit over the range of from about -60 F. to +200 F., consisting essentially of polyvinyl chloride resin, a stabilizing agent, an ammonium perchlorate oxidizing agent and a plasticizing agent, the improvement being in using 5-20% by weight di-normal octa-decyl adipate as the plasticizing agent.

5. An explosive composition consisting essentially of an ammonium perchlorate oxidizer (S0-85% by weight), polyvinyl chloride resin (5-20% by weight) and di-nocta-decyl adipate (5-20% by weight), wherein the ratio of polyvinyl chloride resin to di-n-octa-decyl adipate is within the range of about 3 to 2 and 2 to 3.

6. ll`he composition of claim 5, wherein the ratio is 1.0 to 1.0.

7. An explosive composition containing, as the essential ingredients, in percent by weight:

Di-n-octa-decyl adipate 9.75 Ammonium perchlorate 80.00 Ferro 1212-A 0.50

Total 100.00

wherein the composition has a burning rate increase, over a Wide temperature range of about 0.06% per degree Fahrenheit.

9. An explosive composition containing, indicated as percent by weight:

Percent Polyvinyl chloride resin 12.25 Di-n-octa-decyl adipate 12.25 Ferro 12l2-A .50 Ammonium perchlorate 75.00 Total 100.00

10. An explosive composition containing, indicated as percent by weight:

Percent Polyvinyl chloride resin 13.50 Di-n-octa-decyl adipate 13.50 Ferro 1212-A .50 Ammonium perchlorate 72.50

Total ll. An explosive composition containing, indicated as percent by weight:

Percent Polyvinyl chloride resin 13.45 Di-n-octa-decyl adipate 13.45 Ferro 12l2-A .50 Ammonium perchlorate 72.50 Carbon .10

Total 100.00

12. An explosive composition containing, indicated as percent by weight:

Percent Polyvinyl chloride resin 13.25 Di-n-oct-a-decyl adipate 13.25 Ferro 12l2-A .50 Ammonium perchlorate 72.50 Carbon .50

Total 100.00

13. An explosive composition containing an ammonium perchlorate oxidizer, polyvinyl chloride resin and a plasticizer, the improvement being in the use of from 5-20% by weight di-normal octa-decyl adipate a-s the plasticizer and in the addition of up to about 1% by weight carbon to increase the burning rate of the composition.

References Cited in the file of this patent UNITED STATES PATENTS Weil Dec. 27, 1960 Rumbel et al Aug. 22, =1961 

1. AN EXPLOSIVE COMPOSITION CONSISTING ESSENTIALLY OF POLYVINYL CHLORIDE RESIN, AMMONIUM PERCHLORATE AND A PLASTICIZER, THE IMPROVEMENT BEING IN THE USE OF FROM 5-20% BY WEIGHT DI-NORMAL OCTA-DECYL ADIPATE AS THE PLASTICIZER. 